As a conventional short-circuit isolator, there is known “short-circuit detection means for detecting the short circuit of a line when an input line voltage of the line is equal to or lower than a predetermined threshold line voltage” (see, for example, Japanese Patent Application Laid-open No. Sho 63-19097 (pages 3 and 5, FIG. 1)).
In the technology described in Japanese Patent Application Laid-open No. Sho 63-19097, when the voltage of the line is equal to or lower than the predetermined threshold line voltage, the short circuit is detected and a short-circuit section is disconnected. When the voltage of the line is higher than the predetermined threshold line voltage, the recovery from short circuit is detected and the disconnected section is reconnected.
However, the threshold line voltage for detecting the short circuit is equal to the threshold line voltage for detecting the recovery from short circuit, and hence it takes time to reconnect the section disconnected by the short-circuit detection means after the actual recovery from short circuit.